Tiny, Strange Primate Fossil Unearthed in Coal Mine

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The fossilized jaw of a pint-size primate that lived about 35
million years ago in Asia has been unearthed in Thai coal mines.

The new species, dubbed Krabia minuta, after the Krabi
coal mines where it was found, was an ancient, extinct member of
a group of primates called anthropoids, which includes the
ancestors to all monkeys and apes, including humans. Even so, the
creature showed peculiar features, including its distinct molars,
not seen in other members of this primate group.

"The Asian anthropoids were probably more diversified than what
we know today and also probably played a more important role in
the origin of the modern crown anthropoids than we suspected,"
said study co-author Jean-Jacques Jaeger, a paleontologist at the
Université de Poitiers in France.

Simian evolution

Though humans came from Africa, anthropoids, precursors to
monkeys and humans, likely emerged from Asia. Fossil anthropoids
have been found in China dating to 45 million years ago and in
Southeast Asia as far back as 40 million years, yet similar
species only appear in Libya in Africa around 38 million years
ago.

Scientists have been perplexed by how these
ancient simians made it out of Asia to Africa — an impressive
journey considering that, at the time, Africa was separated from
Asia by the Tethys Sea, which was bigger than the Mediterranean
Sea, said Christopher Beard, a vertebrate paleontologist at the
Carnegie Museum of Natural History in Pittsburgh, who was not
involved in the study.

One hypothesis is that
ferocious cyclones ripped out whole chunks of land and trees
in Asia — complete with primates and rodents clinging to the
branches — and set those mini-islands adrift at sea. Those
islands eventually floated to Africa, and the few tree-dwellers
that survived then colonized the new continent, Beard said.

Yet Asian fossils that could help test this hypothesis have been
hard to come by.

"The problem for paleontologists is that when you've got so much
foliage everywhere, like a jungle, it's almost impossible to find
fossils," because the foliage covers up earth where the fossils
would be exposed, Beard told LiveScience.

Coal mine find

Jaeger and his colleagues excavated in the Krabi coal mine in
Thailand, where the earth was already exposed. Paleontologists
have discovered a trove of fossils from the area, including a
20-lb. (9 kilograms) anthropoid known as Siamopithecus.

The team unearthed part of a jaw and teeth from a tiny creature
that likely weighed just half a pound. Based on the tooth
geometry, the creature was definitely an anthropoid, though one
very different from any other kinds previously known.

"The molar teeth of Krabia are very peculiar and
indicate a diversified food made of soft fruits and or gum. This
diet is very different from the other known southeast Asian
anthropoids," who ate either insects or hard foods such as
nuts, Jaeger said.

The team hypothesizes that the little simian is a (albeit odd)
member of a group called amphipithecids, an extinct group of
anthropoids that lived in Southeast Asia.

But because so little of the creature's body was preserved, Beard
isn't certain of that classification.

"Reasonable people could disagree about what this fossil is and
where it fits on the
family tree of primates," Beard said.

That doesn't detract from the fossil's significance.

"It's one of a very few number of fossils that have come from
there, and we have reason to think that Southeast Asia was a real
epicenter for primate evolution at that time," Beard said.

The findings were detailed today (Oct. 1) in the journal
Proceedings of the Royal Society B.